Prosthetic devices may be placed in vessels and ducts for a number of medical procedures. Typically, placement of the prosthetic devices into the vessels and ducts functions to maintain an open passage through the vessel or duct. For example, where a biliary or pancreatic duct becomes occluded, it is often desirable to facilitate drainage through the duct by the placement of a tubular prosthesis within the occluded area. In some procedures, one or more stents have been used to maintain an open passage.
The passageways into which the stents are placed may change shape and move in response to bodily movement of the patient. Stents designed for placement in these passageways are flexible to accommodate movement of the passageway. Stents are commonly made of polymers or metals, typically a shape memory ahoy, and may include flaps or barbs at each end of the stent which serve to prevent migration and retain the stent in place. Some stents may have various pre-formed retaining configurations, such as pigtails or spirals, to help maintain the stent in position. Stents have also been formed into various expandable configurations so that, when the stent has reached the occluded area, the stent is expanded to press outwardly against the ductal wall and to thereby maintain its position within the duct.
During the placement procedure, especially when more than one stent is being positioned within the duct, the stents may change position. For example, when one stent is positioned within the duct and a second stent is placed beside the first stent, the first stent may be pushed too far into the duct during positioning of the second stent.
There is a need for an improved stent which can be atramatically placed within duct and that can be maintained in position or easily repositioned when additional stents are placed within the same duct.